I've never been the fastest at typing messages and some people do not reply straight away.

我一直以来打字都不快，而且有的人并不会马上回复你。

youdao

Using the Short Messaging Service (SMS) functions on mobiles, people with hearing difficulties can communicate by typing messages into their phones.

BBC: Deaf go mobile phone crazy

And users can see when people are typing or when they sent messages, as they do with instant messengers.

FORBES: Connect

When the young members of Generation-i use their phones to send text messages, the small keyboards make typing awkward and abbreviations even more important: "b4n" (bye for now), "cu" (see you).

WSJ: David Gelernter: The Pros and Cons of Cyber-English